I wish the manufacturers were clearer on how to break in the engine. Here is an exerpt OS .12 TZ manual:

Excessively rich running and prolonged low speed running mean nothing. Prolonged low speed running and low temperature running may result in the oil in the fuel being gelled and piston/liner being agglutinated.

Try to make time to run the car at full throttle. Lengthen full throttle running time gradually. When the car can run full throttle with rich mixture at the straight, close the needle-valve a little. Repeat this procedure until the car runs at the maximum speed at the latter straight course.

The following procedure is suitable for these engines when the O.S. T-1040 tuned silencer and a fuel containing up to 30% nitromethane are used.

When the engine starts, first allow it to operate in short runs at the very rich starting settings, with the glowplug battery still connected and the driving wheels clear of the ground. The rich mixture will, under these conditions, provide adequate lubrication and cooling, indicated by profuse smoke from the exhaust.

Attention: It is vitally important to set the throttle at the correct position before starting the engine. If the engine is allowed to run with the throttle too far open under ''no load'' conditions (i.e. with the driving wheels not in contact with the ground) it will rapidly over-heat and may be
seriously damaged.

Next, disconnect the glowplug battery and try running the car on the track. If the engine stalls, open the throttle fractionally, but try to keep the engine running as rich as possible: if it stops because of being excessively overrich, close the Needle-Valve 15° and try again.

If you've never broken in an engine before, this is incredibly vague. What length of time is prolonged? Agglutinated is just too hilarious. Short runs with the wheels off the ground? Does this mean to idle the car? And what exactly are short runs? And have you ever been able to start a car with the throttle full open? Not me. In fact it's the first thing I spot check if the car won't start. And yeah, the guy at my LHS told me to buy the RDLogics Pipe and 20% fuel. What's up with this T-1040 pipe and 30% fuel? Try to make time to run the car at full throttle? Am I so busy that I need to schedule an appointment? What duration of time would be considered gradually? If you put the engine on the ground and it stalls, don't you have to restart it again? And why in the world would you open the throttle more? Doesn't the stall mean that your engine is loading up because it's too rich? Yeah, let's keep on opening that puppy until it doesn't stall. Oh and then if you've turned it too far (How do you determine that? When the screw pops out?), start turning it 15 degrees at a time until it doesn't stall. Great. Just great.

You can probably get good advice from someone that has the same engine, that has successfully broken in more than a few engines, but if you get advice from someone that has never run your engine before or it's his first engine, it's a toss up. One experienced racer running a JP motor told me to butt the front of the car up against a wall and let it idle for 10 tanks. Another guy said to just start running it on the track, but drive slowly. And another guy told me to just follow the instruction manual that came with the car.